The present invention relates to apparatus for monitoring the condition of endless belts which consist of or contain a filamentary material. More particularly, the invention relates to improvements in apparatus for monitoring the condition of endless belts of woven textile or other filamentary material which can be utilized in the tobacco processing industry to transport streams of particles consisting of natural tobacco, reconstituted tobacco, imitation tobacco and/or filter material. Still more particularly, the invention relates to improvements in apparatus which can be utilized with advantage to monitor the condition of foraminous belt conveyors, particularly of the type commonly used in cigarette rod making machines to transport endless streams of fragmentized tobacco leaves.
The endless belt conveyor which is utilized in a cigarette rod making machine to build up and transport a continuous stream of fragmentized smokable material is subjected to pronounced stresses, particularly in a modern high-speed cigarette maker which turns out in excess of 8,000 plain cigarettes per minute. As a rule, particles of smokable material are showered onto one side of the running belt conveyor while the other side travels along a perforated wall forming part of a suction chamber so that the showered particles are attracted to the one side and advance with the belt conveyor. Such conveyor is trained around numerous pulleys and is tensioned so as to ensure predictable advancement of its particle-conveying reach along a predetermined path. The tensioning device subjects the belt conveyor to pronounced stresses, and additional stressing of the belt conveyor takes place during travel between closely adjacent sidewalls in the tobacco channel as well as during flexing at the wrapping station where the stream of smokable material is draped into a web of cigarette paper or the like. The belt conveyor is caused to travel at an elevated speed, particularly in a modern cigarette maker, so that its life span is relatively short. It has been found that discrete filaments of a textile belt conveyor are likely to undergo extensive wear and to ultimately break as a result of the aforediscussed tensioning in a cigarette maker. The end portions of broken filaments project from the belt conveyor and are likely to interfere with proper transport of smokable material and particularly with predictable transfer of successive increments of a continuous stream of smokable material from the belt conveyor onto another conveyor. At the aforementioned operating speeds, even a short-lasting interruption of or interference with the operation of the stream forming unit in a cigarette maker can entail huge losses in output.